Since this machine is only a development server, I more recently decided to turn the same machine into a VMware VM, running locally (in VMware Fusion 4 on my MacBook Pro). Here, I document the steps necessary for that transformation.
The domU in question is running Ubuntu 10.04. I believe some of these steps would need to be amended for later Ubuntu versions (and some other Linux flavours), which use Grub 2.
Retrieve the logical volume
First we need to grab the LVM volume that represents the domU’s disk from the Xen machine. I shut down the domU in preparation for this, but if uptime was important I could have taken an LVM snapshot instead.
On the Xen dom0 I temporarily make the volume world-readable (
sudo chmod go+r /dev/vg0/my-domu-root), then retrieve it from my laptop with
ssh email@example.com -C "dd if=/dev/vg0/my-domu-root bs=1M" | dd of=my-domu.img
Convert to VMDK
What we’ve just downloaded is a raw partition, and VMware wants a disk in VMDK format, so we use
qemu-img to convert it.
qemu-img convert -p -O vmdk my-domu-root.img my-vm.vmdk
(I initially tried to do this on my Mac, using
brew install qemu to get the
qemu-img binary onto my Mac, but for no obvious reason the conversion kept freezing part-way. So in the end I did this step on the Xen dom0 instead, installing the tool with
sudo aptitude install qemu-utils, and then copied the converted file back over with SSH).
Create new VMware VM
Now in Fusion, I create a new VM. Amongst other options, I add two hard drives: (1) a new drive, sized large enough to accommodate the domU drive data + some swap space, and (2) the converted drive from the domU.
We can’t boot from the converted domU drive for several reasons. Most fundamental of these is that it’s just a raw partition, so our first job is to copy it into a partition on a complete (virtual) drive.
Boot GParted Live disk
I download the GParted Live disk .iso, and set that as the contents of the VM’s DVD drive. Now I boot the VM.
Partition new drive
Using GParted, I create a partition map on the new, empty disk (keeping the default type, ‘msdos’). I create an ext4 primary partition, matching the filesystem of the domU drive and slightly larger than it. I create a swap primary partition to fill the remaining space on the new disk, and apply.
At this point, the new drive is appearing as
/dev/sda, with the new ext4 partition as
/dev/sda1 and swap as
/dev/sda2. The domU drive is appearing as
/dev/sdb and is a partition in itself.
Be sure to use the correct device paths for your system! If I were doing this again, I’d probably use UUID-based paths instead.
Copy domU data
Now I open Terminal and copy the data from the domU partition to the blank ext4 partition on the new drive, and resize the filesystem to fill that new partition.
sudo su dd if=/dev/sdb of=/dev/sda1 bs=10M e2fsck -f /dev/sda1 resize2fs /dev/sda1
I then set the boot flag on
/dev/sda1 in GParted.
After making key system directories accessible from the domU partition, we
chroot to make that our new root.
mount /dev/sda1 /mnt mount --bind /sys /mnt/sys mount --bind /proc /mnt/proc mount --bind /dev /mnt/dev chroot /mnt
Get Grub and a kernel
The domU I am moving in this case already has Grub and a kernel installed, as it was being booted using
pygrub on the dom0.
However, for a domU that has been booted with an external kernel — a domU copied directly from Linode, for example — one would need to install both of these at this point. I believe the following command would do the job, assuming you have an Internet connection working, but I haven’t tested it.
aptitude install linux-generic-pae linux-headers-generic-pae grub
Fix drive references
There are several places in the domU configuration that currently refer to
/dev/xvdb as the root and swap partitions respectively, and these now need changing.
We amend the drive specifications in
sed -i -e 's|/dev/xvda|/dev/sda1|g' -e 's|/dev/xvdb|/dev/sda2|g' /etc/fstab sed -i -e 's|/dev/xvda|/dev/sda1|g' -e 's|/dev/xvdb|/dev/sda2|g' /etc/mtab sed -i -e 's|/dev/xvda|/dev/sda1|g' /boot/grub/menu.lst
- In spite of it being a file that’s usually dynamically created, it’s important to include
/etc/mtab, since that’s where Grub will look to discover our root partition.
menu.lstis confusing and messy. Parts of it are automatically generated while other parts are not, and various lines that are ostensibly commented out are in fact active, including the kernel options (# kopt) line that’s crucial here.
Install and update Grub
Then we install Grub in the boot record, and get it to update
grub-install /dev/sda update-grub
At this point your domU ought to be bootable in VMware but would probably hang, waiting on the Xen hypervisor console
hvc0 which doesn’t now exist. So:
cp /etc/init/hvc0.conf /etc/init/tty0.conf sed -i -e 's|hvc0|tty0|g' /etc/init/tty0.conf mv /etc/init/hvc0.conf /etc/init/hvc0.conf.disabled
That should be everything necessary to reboot into your domU on VMware.
shutdown -h now
Remove the original domU disk from the VM, and also the GParted live disk .iso from its virtual DVD drive. Then restart it.
Assuming your new VM boots up OK, you may now need to tweak networking settings in
/etc/resolv.conf, and to tweak
Apache conf files, and so on.